In WO 00/37159, a disc filter is described in which liquid is passed through one end of a rotary drum and on through openings in the periphery of the drum, radially outwards to at least one filter element. Each filter element includes a filter frame, which is covered by filter cloth on either side of the filter frame. The disc filter also includes a flushing ramp, which extends parallel to the centre axis of the disc filter, outside the outer edge of the disc filter. From the flushing ramp, a number of smaller flush tubes extend in a radial direction. The flush tubes are inserted between parallel filter elements. Pressurised cleaning fluid is sprayed through the flushing ramp and the flush tubes, out through at last one spray nozzle towards the surface of the filter cloth, in a direction opposite the filtering direction, to clean away possible accumulations from the filter cloth. The accumulations are flushed back inside the filter element and passed to a trough, which diverts the accumulations. The spray nozzles may be arranged directed towards two parallel filter elements for simultaneous cleaning of the filter elements.
A flushing device of this type requires that the nozzles are placed at a certain distance from the filter cloth, such that sufficient diffusion of the cleaning fluid is achieved to give sufficient cleaning effect, especially in more clogged-up areas of the filter cloth.
In order to have room for inserting a flush tube and at the same time efficiently cleaning two parallel filter elements by placing the nozzles at said distance, it is necessary that the filter elements are arranged spaced a certain distance from each other.